Several methods for the preparation of silicon oxide powder are known in the prior art. Patent Document 1 discloses a method including heat treating a charge of silicon dioxide base oxide powder in a reduced pressure, non-oxidizing atmosphere to generate SiO vapor, and condensing the SiO vapor in a gas phase, thereby continuously forming fine amorphous SiO particles with a size of 0.1 μm or less. Patent Document 2 proposes a method involving heating a silicon raw material for evaporation and depositing the vapor on a surface of a substrate having a coarse structure. Patent Document 3 discloses a method including feeding a powder feed containing silicon dioxide to a reaction chamber, producing silicon oxide gas, depositing on a surface of a cool substrate, and continuously recovering the silicon oxide deposit.
The method of Patent Document 1 is capable of continuous production, but fails to produce high purity silicon oxide powder because the SiO powder produced is a submicron-size powder which undergoes oxidization when taken out in the air. The method of Patent Document 2 can produce high purity silicon oxide powder, but does not lend itself to mass-scale production since it is of batchwise design. As a consequence, the silicon oxide powder becomes expensive. Although the method of Patent Document 3 can recover high purity silicon oxide powder in a continuous manner, the scraper used is based on a rotating unit which includes bearings which are less resistant to long-term operation, failing to maintain gas tightness.